The nicotine receptor in brain is the target site for the addictive properties of cigarette smoke. In addition, the nicotine receptor plays a role in cognition (i.e., thought processing). Patients with Alzheimer's disease have markedly reduced levels of nicotine receptors in brain, and drugs which interact with the nicotine receptor improve cognitive function in patients with this disorder. Finally, other illnesses with abnormalities in cognition (e.g., schizophrenia and Parkinson's disease) may well have reduced levels of nicotine receptors in brain. We have developed a probe that labels and measures the levels of nicotine receptors in the living human brain. During this past year, we brain imaging studies with this probe in healthy subjects and will extend the studies shortly to patients with Parkinson's disease, Alzheimer's disease, and schizophrenia. New findings in this research may lead to improved treatment of the cognitive deficits found in these disorders. As of September 2004, we completed acquisition of the brain scans of the nicotine receptor in Parkinson's and Alzheimer's disease. Preliminary analysis shows markedly reduced number of these receptors in both disorders. We will complete the analysis in the next 2-3 months and submit our findings for publication.